The economic climate of the petroleum industry demands that oil companies continually improve their recovery systems to produce oil and gas more efficiently and economically from sources that are continually more difficult to exploit and without increasing the cost to the consumer. One successful technique currently employed is the drilling of horizontal, deviated, and multilateral wells, in which a number of deviated wells are drilled from a main borehole. In such wells, as well as in standard vertical or near-vertical wells, the wellbore may pass through various hydrocarbon bearing zones or may extend through a single zone for a long distance.
One manner of increasing the production of such wells is to perforate the well production casing or tubing in a number of different locations, either in the same hydrocarbon bearing zone or in different hydrocarbon bearing ones, and thereby increase the flow of hydrocarbons into the well. However, this manner of production enhancement also raises reservoir management concerns and the need to control the production flow rate at each of the production zones. For example, in a well producing from a number of separate zones, or lateral branches in a multilateral well, in which one zone has a higher pressure than another zone, the higher pressure zone may produce into the lower pressure zone rather than to the surface. Similarly, in a horizontal well that extends through a single zone, perforations near the “heel” of the well (nearer the surface) may begin to produce water before those perforations near the “toe” of the well. The production of water near the heel reduces the overall production from the well. Likewise, gas coning may reduce the overall production from the well.
A manner of alleviating such problems may be to insert a production tubing into the well, isolate each of the perforations or lateral branches with packers, and control the flow of fluids into or through the tubing. Typical flow control systems provide for either on or off flow control with no provision for throttling of the flow. To fully control the reservoir and flow as needed to alleviate the above-described problems, the flow must be throttled.
A number of devices have been developed or suggested to provide this throttling although each has certain drawbacks. Note that throttling may also be desired in wells having a single perforated production zone. Specifically, such prior devices are typically either wireline retrievable valves, such as those that are set within the side pocket of a mandrel or tubing retrievable valves that are affixed to the tubing.
A prior method of operating these downhole flow control devices is with a mechanical indexer (some times referred to as a J-slot device). Convention mechanical indexers include an indexer pattern that defines a predetermined sequence of incremental positions of the valve at and between the open and closed position. Thus, to operate the valve to a position that precedes the current valve position in the predetermined sequence, the valve must be cycled through the predetermined sequence to reach the preceding position. The requirement of having to actuate through the predetermined sequence to reach a desired valve position can result in well or formation damage.
Therefore, it is a desire to provide a mechanical indexer and system that facilitates actuating a valve from a current position in a predetermined sequence of valve positions, to a previous cycle position without having to actuate through all of the intervening subsequent valve positions in the predetermined sequence. It is a further desire to provide an indexing device that that has a primary path for actuating a valve through a predetermined sequence of incremental positions at and between open and closed positions and one or more alternative paths to actuate the valve from a current position to a preceding position in the predetermined sequence of incremental positions.